A. Field of Invention
This invention pertains to the art of methods and apparatuses regarding the manufacture of vehicle drive trains, and more specifically to the art of methods and apparatuses regarding ventilation or breather systems of vehicle drive train driveline components.
B. Description of the Related Art
It is known to use on-demand four wheel drive systems with sport utility vehicles. These sport utility vehicles allow for a relatively reduced weight and increased fuel efficiency without sacrificing four wheel drive performance characteristics. Commonly, the on-demand four wheel drive system employs a clutch mechanism inside the rear differential housing as a torque transfer device. It is known that most driveline components, such as the rear differential, comprise interior components, located within a differential housing assembly, that are required to rotate at very high speeds. These interior components are capable of reaching rotational speeds in excess of 5,000 rotations per minute (rpm) during operation of the associated vehicle. These components require constant immersion in a lubricating fluid and commonly, are bathed in a fluid sump. The interior portions of the differential housing assembly often undergo severe temperature changes ranging from atmospheric temperature to considerably higher temperatures dependent upon the severity of use. Due to the differential housing being generally sealed to prevent loss of lubricant and to prevent foreign particles from entering the interior portion of the housing, the noted temperature changes causes corresponding temperature changes in the lubricant. These temperature changes are reflected in pressure changes within the housing. The temperature and pressure changes can inflict severe strain on the housing seals resulting in premature wear of and even complete failure of the seals. In addition, the high temperatures sustained in pressure build-up within the housing can be detrimental to the moving parts within the housing in causing premature wear or failure of these parts and in addition can undesirably heat other assemblies located near the housing.
It is known to use a ventilation system in conjunction with a vehicle driveline component such as the rear differential. The ventilation system vents the high pressure building within the interior portion of the driveline component to the atmosphere in order to allow the components to operate at or as near to atmospheric pressure as possible. The operation of the driveline component at or near atmospheric pressure ensures the longer life of the seals within the driveline components. The inlet to the ventilation system must be located in a dry, vented area in order to meet performance and marketability requirements. The inlet must be located in a position that does not permit water or other debris to enter through the inlet during vehicle operations, specifically, four wheel drive operations such as off-road driving, water fording, and boat launching. Conventionally, the inlet is coupled to the underside portion of the vehicle body and during four wheel driver operations, the inlet is often positioned under or surrounded by water.